1. Field of the Invention
This invention relates to pumping systems particularly useful for employing a relatively high pressure process fluid for pumping the same or another fluid from a relatively low pressure to a relatively high pressure after intervening treatment, and for process circulation of the process fluid at a rate governed by a needle valve controlled diaphragm-type pilot valve which is preferably an astable pneumatic amplifier. More particularly, the pumping system of the invention includes pumping elements which utilize the pressure-volume energy of a relatively high pressure process fluid to circulate this process fluid through a relatively low pressure fluid treatment zone, and then return it at elevated pressure to a zone of high pressure utilization in the process.
2. Brief Description of the Prior Art
Pumps have been devised which are particularly useful for circulating a liquid, such as a desiccant, in gas-liquid process systems having zones of the process within the circulation cycle under different pressures. Many of these are simple pumps of low overall efficiency in the process by reason of the fact that they do not utilize the pressure-volume energy available in circulated pressurized fluids which are used at elevated pressure at some point in the process, and are treated or utilized at a reduced pressure at a different point in the process. In such cases external power for driving the pump is used to repressure the fluid after treatment and preparatory to reuse.
One widely used pumping system devised to make use of the pressure-volume energy in a process fluid initially used in a relatively high pressure zone, then treated at a relatively low pressure, and finally repressurized and returned to the high pressure zone, is that which is illustrated and described in Kimmell U.S. Pat. No. 2,990,910. The Kimmell pump functions to circulate a desiccant liquid in a cycle which includes a high pressure vessel and a low pressure vessel in a way such that the proper liquid level is maintained in the high pressure vessel during the operation of the process. The Kimmell pump contains an internal pilot valve and pump transfer valve which in turn control the operation of the power pistons included in the pump. The construction of the pump is such that no stuffing boxes or pressure barriers are exposed to the atmosphere, thus eliminating the chance of any of the fluids passed through the pump being lost.
A snap action diaphragm-type control valve utilized to actuate and control the speed of operation of a pump is disclosed in Williams U.S. Pat. No. 3,387,563. In the control valve of Williams, a diaphragm is reciprocated in response to the pressure of a control fluid charged to the valve. A needle valve subassembly forming a part of the control valve is used to selectively vary the rate at which fluid pressure builds up on one side of the diaphragm. A ball check valve is provided within the control valve which, at the time that the diaphragm is fully displaced by fluid pressure on one side thereof, as built up after flow through the needle valve subassembly, opens to the atmosphere to relieve the pressure back through the needle valve, and thereby allow the diaphragm to return to its original position. The valve thus opens and closes periodically and automatically, according to the setting of the needle valve. The pulsations of the control valve in the manner described is used to control the stroke of a pump to which the valve is connected.